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CN-121975071-A - Cross-linked polyionic liquid block copolymer and preparation method and application thereof

CN121975071ACN 121975071 ACN121975071 ACN 121975071ACN-121975071-A

Abstract

The invention relates to a cross-linked polyionic liquid block copolymer (cPIL-BCPs) and a preparation method and application thereof, belonging to the technical field of polyelectrolyte materials. The invention solves the technical problem of providing a preparation method of a cross-linked polyionic liquid block copolymer, which is applicable to any imidazolyl polyionic liquid prepared by quaternization. The method comprises the steps of S1, preparing a macromolecular chain transfer agent, S2, synthesizing a neutral precursor block copolymer, S3, quaternizing and crosslinking and performing ion exchange to obtain the crosslinked polyionic liquid block copolymer. According to the method, the specific cross-linking agent is adopted for cross-linking, so that the glass transition temperature of the prepared cPIL-BCPs is obviously improved, the thermal decomposition temperature is high, high-temperature residues are more, the thermal stability is high, and meanwhile, the mechanical property of the material is improved. The electrochemical performance of the solid electrolyte can be improved when the solid electrolyte is applied to the solid electrolyte. In addition, the preparation method of the material is controllable, simple in process, wide in application range, good in repeatability and easy for large-scale production.

Inventors

  • NIU YANHUA
  • SUN ZHIYU
  • HE XI

Assignees

  • 四川大学

Dates

Publication Date
20260505
Application Date
20260312

Claims (10)

  1. 1. The preparation method of the cross-linked polyionic liquid block copolymer is characterized by comprising the following steps: S1, preparing a macromolecular chain transfer agent, namely preparing the macromolecular chain transfer agent with a terminal modified with a chain transfer agent group in an inert atmosphere, wherein the macromolecular chain transfer agent comprises an electrically neutral polymer chain segment; S2, synthesizing a neutral precursor block copolymer, namely dissolving the macromolecular chain transfer agent obtained in the step S1, monomer 4-vinylbenzyl chloride and an initiator in a second organic solvent under inert atmosphere for polymerization reaction, and purifying to obtain the neutral precursor block copolymer; S3, quaternization crosslinking and ion exchange, namely dissolving the neutral precursor block copolymer obtained in the step S2 and a crosslinking agent 1,3, 5-triisoimidazolyl benzene into a third organic solvent for reaction, then adding an imidazole derivative for continuous reaction, finally adding lithium salt for reaction, and purifying to obtain the crosslinked polyion liquid block copolymer.
  2. 2. The method for preparing a cross-linked polyionic liquid block copolymer according to claim 1, wherein the chain transfer agent in the S1 step is 2- (dodecyl trithiocarbonate group) -2-methylpropanoic acid; The number average molecular weight of the charge neutral polymer in the step S1 is 2-200 kDa, and the charge neutral polymer in the step S1 is preferably polyethylene oxide, polystyrene or polydimethylsiloxane; The initiator in the step S2 is an initiator for free radical polymerization of vinyl-containing monomers, and preferably the initiator in the step S2 is azobisisobutyronitrile, azobisisoheptonitrile or dibenzoyl peroxide; the lithium salt in the S3 step is lithium bis (trifluoromethanesulfonyl) imide, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate or lithium tetrafluoroborate; the imidazole derivative in the step S3 is 1-methylimidazole, 1-butyl-3-methylimidazole or 1, 3-diethylimidazole.
  3. 3. The method for producing a crosslinked polyionic liquid block copolymer according to claim 1, wherein in step S1, the molar ratio of the charge neutral polymer to the chain transfer agent is1 (3-5), and preferably the molar ratio of the charge neutral polymer to the chain transfer agent is 1:3.
  4. 4. The preparation method of the cross-linked polyionic liquid block copolymer according to claim 1, wherein in the step S1, the specific method for preparing the macromolecular chain transfer agent is that the chain transfer agent and oxalyl chloride are dissolved in a first organic solvent for reaction, then hydroxyl-containing electrically neutral polymer is added for continuous reaction, and the macromolecular chain transfer agent is obtained after purification, wherein the molar ratio of the chain transfer agent to the oxalyl chloride is (2-4): 5, and the molar ratio of the chain transfer agent to the oxalyl chloride is preferably 3:5.
  5. 5. The preparation method of the cross-linked polyionic liquid block copolymer according to claim 1, wherein in the step S1, the specific method for preparing the macromolecular chain transfer agent is that a polymerization monomer of an electrically neutral polymer, the chain transfer agent and an initiator are dissolved in a first organic solvent together to carry out RAFT polymerization reaction, and the macromolecular chain transfer agent is obtained after the reaction is finished and purified, wherein the molar ratio of the chain transfer agent to the initiator is 1 (1-2), and the molar ratio of the chain transfer agent to the initiator is preferably 1:1.5.
  6. 6. The method for preparing the cross-linked polyionic liquid block copolymer according to any one of claims 1 to 5, which is characterized in that: The molar ratio of the macromolecular chain transfer agent to the initiator in the S2 step is (0.8-1) 1, the dosage of the crosslinking agent in the S3 step is 5-10% of the molar amount of the monomer 4-vinylbenzyl chloride in the S2 step, and the dosage of the imidazole derivative in the S3 step is 3-5 times of the molar amount of the monomer 4-vinylbenzyl chloride in the S2 step; preferably, the molar ratio of the macromolecular chain transfer agent to the initiator in the S2 step is 1:1, the amount of the crosslinking agent in the S3 step is 5% of the molar amount of the monomer 4-vinylbenzyl chloride in the S2 step, and the amount of the imidazole derivative in the S3 step is 3 times of the molar amount of the monomer 4-vinylbenzyl chloride in the S2 step.
  7. 7. The preparation method of the cross-linked polyionic liquid block copolymer according to any one of claims 1 to 5, wherein the first organic solvent is at least one selected from dichloromethane, toluene and tetrahydrofuran, the second organic solvent is at least one selected from dimethyl sulfoxide, toluene and xylene, and the third organic solvent is at least one selected from dimethyl sulfoxide, N-dimethylformamide and acetonitrile.
  8. 8. The preparation method of the cross-linked polyionic liquid block copolymer according to any one of claims 1 to 5, wherein in the step S2, the polymerization reaction temperature is 75-85 ℃ and the reaction time is 15-30 hours, in the step S3, the reaction temperature is 75-85 ℃, the neutral precursor block copolymer and the cross-linking agent are dissolved in a third organic solvent for reaction for 15-30 hours, imidazole derivatives are added for continuous reaction for 15-30 hours, and lithium salt is added for reaction for 36-50 hours; Preferably, in the step S2, the temperature of the polymerization reaction is 80 ℃, the reaction time is 24 hours, in the step S3, the temperature of the reaction is 80 ℃, the neutral precursor segmented copolymer and the cross-linking agent are dissolved in a third organic solvent for reaction 24 h, imidazole derivatives are added for continuous reaction 24 h, and lithium salt is added for reaction 48 and h.
  9. 9. The crosslinked polyionic liquid block copolymer prepared by the preparation method of the crosslinked polyionic liquid block copolymer according to any one of claims 1 to 8.
  10. 10. Use of the crosslinked polyionic liquid block copolymer according to claim 9 as a solid electrolyte.

Description

Cross-linked polyionic liquid block copolymer and preparation method and application thereof Technical Field The invention relates to a cross-linked polyionic liquid block copolymer, a preparation method and application thereof, and belongs to the technical field of polyelectrolyte materials. Background Polyionic liquids (PILs), also known as polymeric ionic liquids, are a class of polyelectrolyte materials formed by introducing ionic liquid structural units into a polymer chain, or by directly polymerizing ionic liquid monomers by polymerization. Compared with small molecular ionic liquid, the polyionic liquid not only maintains the advantages of high ionic conductivity, wide chemical window, low vapor pressure, nonflammability, physical and chemical stability and the like, but also has good plasticity and mechanical properties of macromolecules. Therefore, since the first synthesis in 1998, polyionic liquids have been widely used in the fields of lithium batteries, supercapacitors, gas separation membranes, self-repairing materials, intelligent response materials and the like. However, PILs, when applied as solid electrolytes, face a ubiquitous contradiction in that it is often desirable to lower the glass transition temperature (T g) of the material and promote movement of ionic carriers and polymer segments in order to increase ionic conductivity, often by "softening" the PIL molecular structure (e.g., introducing flexible spacer chains, using bulky or asymmetric anions, etc.), but these design strategies often significantly weaken the mechanical strength and dimensional stability of the material, making it difficult to meet the mechanical properties of practical devices for electrolyte membranes. This "this trade-off" relationship between ionic conductivity and mechanical properties severely constrains the development of high performance PIL-based solid state electrolytes. To counter this contradiction, researchers have turned to more structurally controllable polyionic liquid block copolymers (PIL-BCPs). PIL-BCPs is typically composed of a polyionic liquid segment that provides ion transport functionality and a neutral polymer segment (e.g., polystyrene, polymethacrylate, etc.) that provides mechanical support. However, the ideal expectation of such simultaneous improvement of ionic conductivity and mechanical strength exists only in microphase-separated systems and requires the formation of certain specific ordered nanostructures (e.g., three-dimensional connected networks), and there is still a contradiction between high ionic conductivity and low mechanical properties for systems with weak ordered and disordered microphase separation. In order to solve the problem that the high ionic conductivity and the high mechanical property are difficult to combine in a weakly ordered and disordered microphase separated polyionic liquid segmented copolymer system, a physical or chemical crosslinking strategy is often adopted in the prior art to enhance the mechanical property of PILs or PIL-BCPs. The cross-linked structure can effectively limit molecular chain movement and improve the rigidity, the thermal stability and the mechanical strength of the material, however, the cross-linked structure can inevitably limit migration movement of ionic carriers while enhancing the mechanical property, so that the intrinsic ionic conductivity of the material is reduced. Therefore, it is often difficult to significantly improve mechanical strength while maintaining sufficiently high ionic conductivity suitable for solid state batteries in the prior art for PIL materials modified by conventional crosslinking methods. Disclosure of Invention Aiming at the defects, the first technical problem solved by the invention is to provide a preparation method which is compatible with mechanical properties and ion conductivity and is applicable to all cross-linked polyionic liquid block copolymers synthesized through quaternization reaction. The preparation method of the cross-linked polyionic liquid block copolymer comprises the following steps: S1, preparing a macromolecular chain transfer agent, namely preparing the macromolecular chain transfer agent with a terminal modified with a chain transfer agent group in an inert atmosphere, wherein the macromolecular chain transfer agent comprises an electrically neutral polymer chain segment; S2, synthesizing a neutral precursor block copolymer, namely dissolving the macromolecular chain transfer agent obtained in the step S1, monomer 4-vinylbenzyl chloride and an initiator in a second organic solvent under inert atmosphere for polymerization reaction, and purifying to obtain the neutral precursor block copolymer; S3, quaternization crosslinking and ion exchange, namely dissolving the neutral precursor block copolymer obtained in the step S2 and a crosslinking agent 1,3, 5-triisoimidazolyl benzene into a third organic solvent for reaction, then adding an imidazole derivative for continuo